1. Field of the Invention
The present invention generally relates to the injection of fluid into underground strata for various purposes with the system including an injector for effective control of injection of fluid into an underground formation by the use of pumps for injection under pressure, or gravity flow depending upon the fluid being injected, the characteristics of the underground formation into which the fluid is being injected and the function of the injection system.
2. Description of the Prior Art
It is well-known to inject fluids into underground hydrocarbon reservoirs or formations for the purpose of recovering additional hydrocarbon liquids. This technique, generally referred to as secondary or tertiary recovery, includes pumping of the fluid into an injection well at a high pressure which requires the use of a plurality and relatively long high pressure pipelines extending from a high pressure pump to a plurality of injection wells. Such techniques, while having some degree of success, have many inherent disadvantages and limitations. For example, the control of the quantity of fluid injected at each individual well has not been too successful. When choking the fluid flow in the system to direct more fluid to a particular well usually results in an increase of resistance or pressure throughout the system and this increase requires a corresponding increase in horsepower at the central pump or pumps in order to maintain volume which in turn increases the pipeline pressure resulting in pipeline failures which, of course, can cause the complete shutdown of the flooding operation. The known techniques also result in high energy consumption relative to the volume of fluid injected due to resistance to flow in the pipeline system which must be overcome by the pumps. Also, relatively poor sweep efficiency of the flooding fluids within the hydrocarbon reservoir occurs due to the limited flexibility of the system, all of which results in unacceptable total losses of hydrocarbons throughout the world. As a result of inefficiencies inherent in the present techniques and the costs involved, there have been many instances in which secondary or tertiary recovery of hydrocarbon fluids from reservoirs has been found to result in large energy and monetary losses, thereby rendering the recovery operation economically unprofitable.
In regard to other problems which are encountered throughout the world, underground water supplies have diminished or become unusable because of excessive use, depletion and the like. However, in many of these areas, at certain periods, there is an excess supply of fresh water which results from rainfall or in neighboring geographical areas, there may be an excess supply of fresh water which could be effectively utilized if supplied to a water depleted area by an economical means. In many instances, underground aquifers and other water bearing strata have been exhausted by excessive removal of underground water without regard to the depletion of the supply. Many efforts have been made to impound excessive water supply by using dams to form surface reservoirs which, of course, are used in many localities but which suffer from extreme loss due to evaporation and can become contaminated as well as utilizing substantial land areas that could be better utilized for other purposes.